Porous ceramic materials have received growing attention in recent years for their potential use as catalyst supports, molten metal filters, diesel exhaust filters, combustion burners, thermal insulation, etc. The specific use of the ceramic will depend on the size of the porous ceramic body, the nature of the porosity (closed or open), and ceramic composition among other factors.
These porous ceramic materials have been made by several methods over the years. A good overview of these methods can be found in an article "Processing of Porous Ceramics" by J. Saggio-Woyansky, American Ceramic Society Bulletin vol. 71, No. 11, November 1992, p. 1674-1682. Two principal methods are a) impregnation of a polymer "sponge" with a ceramic slurry followed by firing to remove the polymer, and b) foaming of a ceramic slurry followed by firing the foam. The sponge technique generally produces open (reticulated) pore structures. The foaming technique may produce reticulate and/or closed (vesiculated) pores depending on the foaming technique used and the conditions employed.
For many catalyst support and biological support applications, it is generally desirable to have a ceramic with predominantly reticulate porosity to increase the surface area of the ceramic which is accessible to the medium surrounding the porous ceramic. Further, it is often desirable that the porous ceramic have combinations of micropores and reticulate macropores to allow greater access to the ceramic surface. Interconnected macropores facilitate the passage of fluid through the ceramic.
For many catalyst and biological support applications, the support is typically placed in contact with a fluid reaction medium or biological medium. In these and other applications, the porous ceramic is often used in the form of beads. Generally, spherical beads are preferred. Unfortunately, the need for such ceramic beads with reticulate macroporosity has been unmet.